This invention relates to a video projector. More particularly, this invention relates to an RGB projector of the type employing a dichroic mirror assembly and separate red, green and blue cathode ray tubes operatively associated therewith.
One of the problems with a video projector of this type has to do with varying the top-to-bottom focussing thereof while maintaining convergence. In order to do this properly, the inclinations of the longitudinal axes of all of the cathode ray tubes (CRT's) must be varied the same amount in the same direction. One technique for accomplishing this has been to mount each CRT in its own mounting bracket, pivotably mount each mounting bracket to permit the inclination of the longitudinal axis of the CRT mounted therein to be varied, and provide a rotatable cam with three identical cam surfaces which coact with individual ones of the mounting brackets. The problem with this arrangement, however, is the lack of restraint of the mounting brackets giving rise to possible damage to the apparatus when it is moved.
The foregoing problem is solved, in accordance with the present invention, by the provision of apparatus that not only permits focussing to be varied while maintaining convergence, but also fully restrains the CRT's via their mounting brackets against unwanted movement.